The present invention relates to a technology for enriching a sound (i.e., musical sound or tone) of an acoustic keyboard instrument.
Usually, an electronic piano has no soundboard unlike an acoustic piano, because the electronic piano is configured to produce electronic sound from a speaker. However, Japanese patent application laid-open publication No. JP2008-292739A discloses a technology of mounting a soundboard on the electronic piano and installing speakers on the soundboard so that by exciting the soundboard with the speakers, a vibration sound is radiated from the soundboard. As a result, the electronic piano can produce not only electronic sounds but also enriched acoustic low-pitched sounds due to radiation of the vibration sounds from the soundboard. The above-mentioned patent literature also discloses that such a technology can be applied to not only the electronic piano but also a case where the acoustic piano is configured not to vibrate any strings (sound-deadening piano).
The sound quality of the acoustic piano largely depends on the vibration characteristics of the soundboard which radiates sounds. Consequently, if any heavy object or device is installed on the soundboard which nobody imagined when the piano was manufactured in plant, the vibration characteristics of the soundboard is changed largely due to an influence of the heavy object or device. As a result, an intrinsic sound quality of the acoustic piano deteriorates.
In a configuration of the above-described prior art technology of installing the speaker, which is a heavy object or device, directly to the soundboard, a weight of the speaker influences the soundboard, and the vibration characteristics of the soundboard is therefore changed largely between before and after the soundboard is mounted. Thus, when the above-described preceding technology is applied to the acoustic piano, the vibration characteristics of the soundboard is changed due to an influence of the speaker so that the intrinsic sound quality of the acoustic piano is influenced and changed, which is a problem.